It has been the custom for many years in the CATV trap and filter industry to focus upon the hermesticity of the device housing when designing the connectors at each end of the housing. This has led to a preference for moisture blocking insulative materials such as glass and thick cross-section pieces of rubber. While these materials typically are very good at preventing moisture from entering the device housing, they create very low impedance zones within the connections which are not matched to the 75 ohm impedance of the CATV system.
While this does not prevent signal transmission to a debilitating degree in analog systems, it does cause a great deal of signal reflection, i.e., high return loss, which can cause debilitating interference in systems which operate digital programming and data within their bandwidth. While some of this reflection may be compensated for by selective tuning of the filter circuit within the housing, it is not sufficient if return loss values of −20 dB or less, i.e., −30 dB, −40 dB, etc., are desired. To achieve these improved levels of return loss, it is necessary to impedance match the connector portions of the housing as close to 75 ohms as possible.
U.S. Pat. No. 6,888,423 (Tresness et al.) and U.S. Pat. No. 6,323,743 (Zelenz et al.) both disclose a solid polypropylene insulator 96b at one end of the housing and a solid low density polyethylene insulator 95 at the other end.
U.S. Patent Application Publication No. 2005/0162238 (Ho) discloses an insulating ring 42 secured within a separating part 41 at one end of the housing.
U.S. Pat. No. 6,794,957 (Shafer et al.) discloses a solid insulator 24 at one end of the housing and a solid deformable rubber seal 20 and a solid insulator 22 at the other end.
U.S. Pat. No. 5,498,175 (Yeh et al.) discloses two insulating members 53 which go on both ends of a contact member 20, with each insulating member 53 consisting of an insulating sleeve 30, a silicone resilient member 52, and an insulating cap 50.
U.S. Patent Application Publication No. 2005/0001697 (Gould et al.) discloses a solid polypropylene insulator 96b at one end of the housing and a solid low density polyethylene insulator 95 at the other end.